1. Field of the Invention
The present invention relates to semiconductor fabrication equipment. More particularly, the invention relates to a device and method for preventing errors in a sensing operation during a wafer cleaning process.
2. Description of Related Art
A wet clean station supplies N2 gas and pure water (DI) to wafers to remove wafer impurities such as polymer particles. Wafers are cleaned in a pure water bath (DI Water Bath) of the wet station. A quartz wet station (Quartz DI Water Bath) includes an optical fiber sensor attached to the outside of the pure water bath. The optical fiber sensor detects whether a wafer is present in the pure water bath.
FIG. 1 is a cross sectional view of a conventional wet clean station having optical fiber sensors 20a, 20b disposed on the outside of the pure water bath 10. Referring to FIG. 1, a conventional wet clean station includes a pure water bath 10. The pure water bath 10 receives a wafer. Pure water is supplied to the pure water bath 10 to clean the wafer. First and second fixing guides 12a, 12b are disposed at the upper and lower portions of the pure water bath 10, respectively, to fix an optical fiber sensor thereto. First and second gas supply pipes 14a, 14b are respectively inserted into the fixing guides 12a, 12b to supply nitrogen (N2) gas to the inner side of the fixing guides 12a, 12b. First and second gas supply boxes 22a, 22b supply the N2 gas through a gas inlet (N2 Input) to a respective one of the first and second gas supply pipes 14a, 14b. The gas supply boxes 22a, 22b discharge the gas from the respective one of the first and second supply pipes 14a, 14b through a gas outlet (N2 Output).
The first gas supply pipe 14a is provided with first and second O-rings 16a, 18a around its outer circumference. The second gas supply pipe 14b is provided with third and fourth O-rings 16b, 18b around its outer circumference. The first and second gas supply pipes 14a, 14b respectively include first and second optical fibers 20a, 20b. The first through fourth O-rings 16a, 18a, 16b, 18b serve to prevent pure water from flowing into the first and second fixing guides 12a, 12b from the outside. The first through fourth O-rings 16a, 18a, 16b, 18b also serve to prevent N2 gas from being discharged from the first and second fixing guides 12a, 12b. The first and second O-rings 16a, 18a, and the third and fourth O-rings 16b, 18b further serve to secure the first and second gas supply pipes 14a, 14b into the first and second fixing guides 12a, 12b, respectively.
The pure water bath 10 of the wet station is supplied with pure water having a temperature of approximately 70xc2x0 C. After cleaning the wafer, the waste water is then discharged, and a robot transfers the wafers from the pure water bath 10 to the next pure water bath. When the wafers are transferred to the next pure water bath of the wet station, the first and second optical fibers 20a, 20b detect whether a wafer is present in the pure water bath 10. During normal operation, the first fiber 20a emits light and the second fiber 20b receives the emitted light when no wafers are present.
Unfortunately, the temperature difference between the pure water (approximately 70xc2x0 C.) and the outside room temperature (approximately 25xc2x0 C.) results in dew forming on the outside surface of the pure water bath 10. Dew also forms inside the first and second fixing guides 12a, 12b. The presence of dew in the fixing guides 12a, 12b prevents the optical sensors 20a, 20b from transmitting and receiving light therethrough. This can result in errors in equipment operation because the system may operate as if wafers are present in the pure water bath 10 even when no wafers are present. If the first and second sensing fibers 20a, 20b experience errors in operation, the robot will stop transferring the wafers into the wet station, resulting in the wafers being dried in air. This causes inferior wafer quality.
To prevent operation error, N2 gas is supplied to the first and second gas supply boxes 22a, 22b through the N2 Inputs. Gas from the gas supply boxes 22a, 22b is supplied to the gas supply pipes 14a, 14b. Gas pressure (for example, 0.2 to 1 Kgf/m2) builds up in the inner side of the first and second fixing guides 12a, 12b. Dew that is formed on the outside of the pure water bath 10 is discharged through the N2 Output due to the pressure created by the N2 gas. In this way, dew formed on the outside of the pure water bath 10 can be removed to prevent sensing errors.
Unfortunately, however, the gas pressure built up in the fixing guides 12a, 12b may cause the gas supply pipes 14a, 14b to become separated from the first and second fixing guides 12a, 12b. It would be desirable to have a device and method that prevented sensing errors. It would further be desirable to have a device and method that prevented unwanted pipe separation while preventing sensing errors.
Accordingly, an object of the present invention is to provide an error-preventing device that prevents errors in the operation of optical sensor units for semiconductor fabrication equipment.
Another object of the present invention is to provide a method for preventing errors in the operation of the optical fiber sensors of the fabrication equipment.
In order to achieve the foregoing objects, a wet clean station according to a preferred embodiment of the present invention includes a pure water bath for receiving pure water or chemicals to remove particles from a wafer. The pure water bath can be further configured to discharge waste water after removing the particles. Gas supply pipes are provided having optical fiber sensors inserted into the gas supply pipes. Fixing guides are disposed on the outside of the pure water bath to fix the optical fiber sensors thereto. Purge output holes are formed at predetermined locations along the fixing guides.
A method for preventing errors in the operation of fabrication equipment is also provided. The fabrication equipment preferably includes a cleaning station and an optical sensor unit. The cleaning station may be pure water bath. The optical sensor unit can include gas supply pipes, fixing guides, and optical sensors. The method includes discharging excess pressure and/or moisture from the optical sensor unit. This can be done, for instance, by forming purge output holes in the fixing guides to permit the expulsion of excess pressure and moisture therefrom.